In recent years, processors called multitask processors (hereinafter collectively referred to as “multiprocessor”), which can handle a plurality of tasks in parallel, are going into use in embedded devices or the like.
In conventional portable devices, processing has been performed with a single processor. However, as the functionality of the portable devices is enhanced, processing is becoming more complicated, and processing with a single processor is becoming difficult.
More specifically, if an attempt is made to achieve high-functionality using a single processor, the single processor has to be run at high clock frequencies, and power consumption increases accordingly. In addition, it would be difficult to deal with a case where a phone must be answered in real time, for example, in such a case where an incoming call is received while moving images are being played in a mobile telephone.
On the other hand, the use of a multiprocessor allows the clock frequency of the device to be lowered, thereby reducing power consumption. Additionally, since a plurality of tasks can be handled in parallel, the use of the multiprocessor is also useful from the viewpoint of real time response.
Incidentally, in some processors for such embedded devices, requests for interrupt handling are relatively frequently made from peripheral devices connected to the embedded device. When an interrupt request is made, interrupt handling is performed: task processing that is being performed by the processor is suspended, and the requested processing is performed. In the interrupt handling, exclusive control is implemented between the task processing and the interrupt handling in order to smoothly switch between the interrupt handling and the task processing.
One example of the prior art of conventional exclusive control between task processing and interrupt handling is Patent Document 1. The invention described in Patent Document 1 is related to exclusive control in a single processor, wherein interrupt handling that does not issue any system call is accepted even during processing in which system calls for calling an OS are issued in the single processor. The invention of Patent Document 1 uses such behavior to reduce wait time of highly urgent interrupt handling.
[Patent Document 1] JP-A-8-297581